This invention relates to windshield wiper apparatus for a motor vehicle which has selectable, plural modes of operation for different weather conditions. In particular, it relates to such apparatus which has a normal mode of operation for light to medium rain or snow and a separate selectable "storm" mode for heavy rain or snow which provides distinct advantages in visibility during such storm conditions.
Typical windshield wiper apparatus provided with today's motor vehicles includes a pair of wipers which sweep across a windshield in tandem with the driver's side blade pivoted at a point below the driver's side of the windshield and the passenger side wiper pivoted at a point to the passenger side of the pivot of the driver side blade. Referring to FIG. 1, the passenger side blade generally sweeps the area GBHI; while the driver side blade sweeps the area EFCD. Normally, two speeds of wiper operation are provided for different weather conditions; but there is no change in the wiper pattern. This arrangement has proven sufficiently successful to be the standard windshield wiper arrangement for small passenger vehicles and works well in almost all weather conditions.
However, most drivers of motor vehicles have occasionally experienced precipitation which collects on the windshield so fast and in such quantity that visibility is greatly diminished even at the high speed of wiper operation and the driver must slow his vehicle greatly or even pull off to the side of the road. The driver may, however, prefer to continue and he would thus welcome a special "storm" mode of operation which he could immediately select to provide improved performance in heavy precipitation.
With respect to the normal wiper operating modes, there appear to be two limitations which are not important in light or medium precipitation but which assume increasing importance as the precipitation becomes heavier. The first is that the blades are designed to clean as great an area of the windshield as possible. They continue to sweep the same area even as their speed is increased in response to heavier precipitation. However, when precipitation becomes so heavy that they cannot keep up with it at high speed, it might be desirable to assign a higher priority to a smaller area of the windshield directly in front of the vehicle operator and increase the cleaning rate in that area of the windshield at the expense of another part of the windshield, particularly the passenger's side. The other factor is that, in the normal mode of operation, the passenger side blade reaches its maximum outer position BG as shown in FIG. 1 and leaves its accumulated residue from the windshield in a line in front of the driver until the driver's blade sweeps the residue to the bottom of the windshield on its reverse wipe. When precipitation is heavy, it would be desirable to positively sweep it out of the driver's main field of vision on each wipe.